Loudness maximization with constrained loudspeaker excursion

Abstract

An original loudness level of an audio signal is maintained for a mobile device while maintaining sound quality as good as possible and protecting the loudspeaker used in the mobile device. The loudness of an audio (e.g., speech) signal may be maximized while controlling the excursion of the diaphragm of the loudspeaker (in a mobile device) to stay within the allowed range. In an implementation, the peak excursion is predicted (e.g., estimated) using the input signal and an excursion transfer function. The signal may then be modified to limit the excursion and to maximize loudness.

What is claimed: 
     
       1. A method of constraining loudspeaker excursion in a mobile station, comprising:
 receiving an input audio signal at the mobile station; 
 transforming, in the digital domain, the input audio signal into a plurality of subband signals in the equal rectangular band (ERB) scale; 
 determining a peak excursion, in the digital domain, of a loudspeaker of the mobile station, for either one or more of the entire ERB subbands or certain portions of one or more ERB subbands; 
 performing signal processing on the subband signals based on the peak excursion and a maximum loudspeaker excursion to limit the excursion of the loudspeaker; and 
 combining and outputting the signal processed subband signals to the loudspeaker. 
 
     
     
       2. The method of  claim 1 , wherein determining the peak excursion of the loudspeaker comprises filtering the subband signals with an excursion transfer function of the loudspeaker. 
     
     
       3. The method of  claim 1 , wherein performing the signal processing maximizes a perceived loudness of the input audio signal. 
     
     
       4. The method of  claim 3 , wherein the perceived loudness of the input audio signal is based on an approximation of a psychoacoustic loudness model. 
     
     
       5. The method of  claim 3 , wherein the perceived loudness of the input audio signal is based on a subband energy of each ERB subband and a specific loudness at each ERB subband. 
     
     
       6. The method of  claim 5 , further comprising:
 determining the subband energy of each ERB subband. 
 
     
     
       7. The method of  claim 6 , further comprising approximating the specific loudness at each ERB subband based on a psychoacoustic loudness model. 
     
     
       8. The method of  claim 1 , wherein performing the signal processing is performed in a frequency domain. 
     
     
       9. The method of  claim 1 , further comprising pre-processing the input audio signal using a limiter and a makeup gain prior to predicting the excursion of the loudspeaker. 
     
     
       10. The method of  claim 1 , wherein the mobile station comprises a mobile device, and the input audio signal comprises a speech signal. 
     
     
       11. An apparatus for constraining loudspeaker excursion in a mobile station, comprising:
 means for receiving an input audio signal at the mobile station; 
 means for transforming, in the digital domain, the input audio signal into a plurality of 
 subband signals in the equal rectangular band (ERB) scale; 
 means for determining a peak excursion, in the digital domain, of a loudspeaker of the mobile station, for either one or more of the entire ERB subbands or certain portions of one or more ERB subbands; 
 means for performing signal processing on the subband signals based on the peak excursion and a maximum loudspeaker excursion to limit the excursion of the loudspeaker; and 
 means for combining and outputting the signal processed subband signals to the loudspeaker. 
 
     
     
       12. The apparatus of  claim 11 , wherein the means for determining the peak excursion of the loudspeaker comprises means for filtering the subband signals with an excursion transfer function of the loudspeaker. 
     
     
       13. The apparatus of  claim 11 , wherein the means for performing the signal processing maximizes a perceived loudness of the input audio signal. 
     
     
       14. The apparatus of  claim 13 , wherein the perceived loudness of the input audio signal is based on an approximation of a psychoacoustic loudness model. 
     
     
       15. The apparatus of  claim 13 , wherein the perceived loudness of the input audio signal is based on a subband energy of each ERB subband and a specific loudness at each ERB subband. 
     
     
       16. The apparatus of  claim 15 , further comprising:
 means for determining the subband energy of each ERB subband. 
 
     
     
       17. The apparatus of  claim 16 , further comprising means for approximating the specific loudness at each ERB subband based on a psychoacoustic loudness model. 
     
     
       18. The apparatus of  claim 11 , wherein performing the signal processing is performed in a frequency domain. 
     
     
       19. The apparatus of  claim 11 , further comprising means for pre-processing the input audio signal using a limiter and a makeup gain prior to predicting the excursion of the loudspeaker. 
     
     
       20. The apparatus of  claim 11 , wherein the mobile station comprises a mobile device, and the input audio signal comprises a speech signal. 
     
     
       21. A non-transitory computer-readable medium comprising instructions that cause a computer to:
 receive an input audio signal at a mobile station; 
 transform, in the digital domain, the input audio signal into a plurality of subband signals in the equal rectangular band (ERB) scale; 
 determine a peak excursion, in the digital domain, of a loudspeaker of the mobile station, for either one or more of the entire ERB subbands or certain portions of one or more ERB subbands; 
 perform signal processing on the subband signals based on the peak excursion and a maximum loudspeaker excursion to limit the excursion of the loudspeaker; and 
 combine and output the signal processed subband signals to the loudspeaker. 
 
     
     
       22. The computer-readable medium of  claim 21 , wherein the instructions that cause the computer to determine the peak excursion of the loudspeaker comprise instructions that cause the computer to filter the subband signals with an excursion transfer function of the loudspeaker. 
     
     
       23. The computer-readable medium of  claim 21 , wherein the instructions that cause the computer to perform the signal processing maximize a perceived loudness of the input audio signal. 
     
     
       24. The computer-readable medium of  claim 23 , wherein the perceived loudness of the input audio signal is based on an approximation of a psychoacoustic loudness model. 
     
     
       25. The computer-readable medium of  claim 23 , wherein the perceived loudness of the input audio signal is based on a subband energy of each ERB subband and a specific loudness at each ERB subband. 
     
     
       26. The computer-readable medium of  claim 25 , further comprising computer-executable instructions that cause the computer to:
 determine the subband energy of each ERB subband. 
 
     
     
       27. The computer-readable medium of  claim 26 , further comprising computer executable instructions that cause the computer to approximate the specific loudness at each ERB subband based on a psychoacoustic loudness model. 
     
     
       28. The computer-readable medium of  claim 21 , wherein performing the signal processing is performed in a frequency domain. 
     
     
       29. The computer-readable medium of  claim 21 , further comprising computer executable instructions that cause the computer to pre-process the input audio signal using a limiter and a makeup gain prior to predicting the excursion of the loudspeaker. 
     
     
       30. The computer-readable medium of  claim 21 , wherein the mobile station comprises a mobile device, and the input audio signal comprises a speech signal. 
     
     
       31. An apparatus for constraining loudspeaker excursion in a mobile station, comprising:
 an excursion predictor for receiving an input audio signal at the mobile station, and for determining a peak excursion, in the digital domain, of a loudspeaker of the mobile station, for either one or more entire ERB subbands or certain portions of one or more ERB subbands; and 
 an excursion limiting signal processor for transforming, in the digital domain, the input audio signal into a plurality of subband signals in the equal rectangular band (ERB) scale, for performing signal processing on the subband signals based on the peak excursion and a maximum loudspeaker excursion to limit the excursion of the loudspeaker, and for combining and outputting the signal processed subband signals to the loudspeaker. 
 
     
     
       32. The apparatus of  claim 31 , wherein the excursion predictor comprises a filter for filtering the subband signals with an excursion transfer function of the loudspeaker. 
     
     
       33. The apparatus of  claim 31 , wherein the excursion limiting signal processor maximizes a perceived loudness of the input audio signal. 
     
     
       34. The apparatus of  claim 33 , wherein the perceived loudness of the input audio signal is based on an approximation of a psychoacoustic loudness model. 
     
     
       35. The apparatus of  claim 33 , wherein the perceived loudness of the input audio signal is based on a subband energy of each ERB subband and a specific loudness at each ERB subband. 
     
     
       36. The apparatus of  claim 35 , wherein the excursion limiting signal processor further determines the subband energy of each ERB subband. 
     
     
       37. The apparatus of  claim 36 , wherein the excursion limiting signal processor approximates the specific loudness at each ERB subband based on a psychoacoustic loudness model. 
     
     
       38. The apparatus of  claim 31 , wherein performing the signal processing is performed in a frequency domain. 
     
     
       39. The apparatus of  claim 31 , further comprising a pre-processor for pre-processing the input audio signal using a limiter and a makeup gain prior to predicting the excursion of the loudspeaker. 
     
     
       40. The apparatus of  claim 31 , wherein the mobile station comprises a mobile device, and the input audio signal comprises a speech signal.